The invention is directed to an apparatus for joining preferably large-area extended workpiece parts by weld seams by means of through-transmission welding as is described generically in the prior published DE 10 2011 055 203.0.
Generally, to carry out through-transmission welding two workpiece parts to be connected to one another are placed together such that they directly contact one another along at least one contact zone. The workpiece parts may be welded together only within such contact zone. The welding connections may be formed at a point, along a line or over a surface. The area along which the weld connection is made is also often referred to as the joining area.
In through-transmission welding, the first workpiece part is transmissive for the laser radiation and faces a laser source. The second workpiece part is absorptive for the laser radiation. The laser radiation penetrates the first workpiece part, impinges on the surfaces of the second workpiece part, is absorbed in an area adjoining the surface and converted into heat energy. The affected area of the second workpiece part fuses which, due to heat conduction, also brings about a fusing of an adjoining area of the first workpiece part and, therefore, a bonding of both workpiece parts to form a workpiece.
If the two workpiece parts are to be connected to one another along a joining area that is smaller than the contact zone, the impingement of the laser radiation must be limited to the joining area so that other areas within the contact zone are not also welded.